The present invention relates generally to an injection-molded solder (IMS) tool assembly and a method of manufacture thereof, and more particularly, but not by way of limitation, to an apparatus that can provide a layer of liquid metal to the inner surface or to the outer surface of a steel pipe.
Carbon steel is one of the most common industrial steels used today. However, this steel rusts easily. To make it into stainless steel, a minimum of 10.5 to 11.0 wt-% chromium (or more) is added to low carbon steel. The addition of chromium makes the steel corrosion resistant. The chromium content of the steel allows the formation of a rough, adherent, invisible, corrosion-resisting chromium oxide film on the steel surface. This formation is called passivation.
Conventionally, if damaged mechanically or chemically, this chromium oxide film is self-healing, provided that oxygen, even in very small amounts, is present. The corrosion resistance and other useful properties of the steel are enhanced by increased chromium content and the addition of other elements such as molybdenum, nickel and nitrogen.
Other metals, in particular Niobium (Nb) and Titanium (Ti) have also been used to create high strength steels where strengthening effects can be obtained already at small additions of Nb. These alloying elements change the properties not by forming strong oxides but by producing specific microstructures in the steel that impart high strength and processability to the steel.
In all of these cases, the alloying metal must be added in bulk. While for instance Cr thus protects the steel throughout its thickness, it is not likely that this effect is needed beyond a certain surface layer. Moreover, prior IMS techniques (injection of molten metal on target substrate) cannot make, for example, coatings of pure Cr, Mo, Ni, Nb, or Ti layers on the surface of carbon steel because the melting temperature of the pure metals is higher than that of carbon steel.